The DRL has been now standardized in Europe and so on, and is becoming standardized in the United States and other countries. As for broadening of light, a light source having light broadening in a right and left direction (horizontal direction) with respect to an upper and lower direction (vertical direction) is required.
As a related-art daytime running light (DRL), there exists an illumination device in which a light emission amount and the number of light emissions in an LED array are changed so that light distribution becomes suitable for daytime running by reducing illumination of a high beam of a headlight (for example, refer to Patent Literature 1). FIG. 14 is a view showing a related-art illumination device for daytime running described in Patent literature 1.
In FIG. 14, the illumination device includes an LED array 11 in which plural LEDs are aligned and a lens 12. Light emitted from the LED array 11 is collimated by the lens 12. Light from LEDs close to an optical axis of the lens 12 becomes light in an optical axis direction, namely, a front direction, and light from LEDs apart from the optical axis of the lens 12 becomes light in a right and left direction, which are emitted from the lens 12. The light distribution becomes suitable for daytime running light by adjusting the light amount of respective LEDs of the LED array 11.
There is also a device in which a line-shaped light source is formed by using a light guide plate (for example, refer to Patent Literature 2). FIG. 15 is a view showing a related-art daytime running light described in Patent literature 2. In FIG. 15, the illumination device includes a high output LED 13 and a light guide plate 14. The light guide plate 14 has prisms 15 formed at an end face thereof.
Light emitted from the high output LED 13 is incident on the light guide plate 14 and propagates inside the light guide plate 14 while being totally reflected. When the light propagating inside the light guide plate 14 is incident on the prisms 15, optical paths of part of the light are bent by the prisms 15, therefore, the light is deviated from the total reflection condition and emitted to the outside of the light guide plate 14. A light 16 is emitted from the entire light guide plate 14.